IMO the actual problem is you want to interact with the people reading what you write.
Without a commenting system, the writing/publishing platform loses a lot of its potential value.
The other problem like other people mentioned is discovery.
Let's take YouTube for an example.
In theory you can make videos and publish them on your own self-hosted website.
But if you post the videos to youtube, you get a bigger chance of people finding out about you.
So, if you want to empower a distributed network of personal websites, you also need a powerful "indexing" engine that continuously fetches and catalogues all the new content being published by all these people for easy discovery.
The other problem is discontinuity between discovery mode and consumption mode.
On YouTube, when you find a video you like, you still see related or recommended videos on the side.
If you have a video index that tries to work like YouTube but redirects to different websites where videos are actually hosted, you get this discontinuity where, once the user visits the actual website where the content is hosted, they are no longer discovering new things on the indexing service.